Magnet arrangement for loudspeaker

ABSTRACT

An electro-dynamic loudspeaker includes a frame, a plurality of magnets and a diaphragm. The frame includes a molded plastic body. The magnets may be molded into the frame in a determined configuration. The frame is mechanically coupled to the diaphragm such that the magnets are a determined distance from the diaphragm. The diaphragm may include a conductor applied to a surface of the diaphragm. The diaphragm may be driven by a motive force created when current passes through the conductor within a magnetic field formed by the magnets. The electrical current may be varied to create an acoustical output from the electro-dynamic loudspeaker.

1. CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/380,001, filed on May 2, 2002; U.S. ProvisionalApplication No. 60/378,188, filed on May 6, 2002; and U.S. ProvisionalApplication No. 60/391,134, filed on Jun. 24, 2002. The disclosures ofthe above applications are incorporated herein by reference.

[0002] This application incorporates by reference the disclosures ofeach of the following co-pending applications which have been filedconcurrently with this application: U.S. patent application Ser. No.______, entitled “Mounting Bracket System,” filed May 2, 2003; U.S.patent application Ser. No. ______, entitled “Film Tensioning System,”filed May 2, 2003; U.S. patent application Ser. No. ______, entitled“Film Attaching System,” filed May 2, 2003; U.S. patent application Ser.No. ______, entitled “Electrical Connectors For Electro-DynamicLoudspeakers,” filed May 2, 2003; U.S. patent application Ser. No.______, entitled “Electro-Dynamic Loudspeaker Mounting System,” filedMay 2, 2003; U.S. patent application Ser. No. ______, entitled“Conductors For Electro-Dynamic Loudspeakers,” filed May 2, 2003; U.S.patent application Ser. No. ______, entitled “Frame Structure,” filedMay 2, 2003; U.S. patent application Ser. No. ______, entitled“Acoustically Enhanced Electro-Dynamic Loudspeakers,” filed May 2, 2003;U.S. patent application Ser. NO. ______, entitled “Directivity ControlOf Electro-Dynamic Loudspeakers,” filed May 2, 2003; and U.S. patentapplication Ser. No. ______, entitled “Frequency Response EnhancementsFor Electro-Dynamic Loudspeakers,” filed May 2, 2003.

BACKGROUND OF THE INVENTION

[0003] 1. Field of Invention

[0004] The invention relates to electro-dynamic loudspeakers, and moreparticularly, to improvements for electro-dynamic loudspeakers andrelated manufacturing methods.

[0005] 2. Related Art

[0006] The general construction of an electro-dynamic loudspeakerincludes a diaphragm, in the form of a thin film, attached in tension toa frame. An electrical circuit, in the form of electrically conductivetraces, is applied to the surface of the diaphragm. Magnetic sources,typically in the form of permanent magnets, are mounted adjacent to thediaphragm or within the frame, creating a magnetic field. When currentis flowing in the electrical circuit, the diaphragm vibrates in responseto the interaction between the current and the magnetic field. Thevibration of the diaphragm produces the sound generated by theelectro-dynamic loudspeaker.

[0007] Many design and manufacturing challenges present themselves inthe manufacturing of electro-dynamic loudspeakers. First, the diaphragm,that is formed by a thin film, needs to be permanently attached, intension, to the frame. Correct tension is required to optimize theresonance frequency of the diaphragm. Optimizing diaphragm resonanceextends the bandwidth and reduces sound distortion of the loudspeaker.

[0008] The diaphragm is driven by the motive force created when currentpasses through the conductor applied to the diaphragm within themagnetic field. The conductor on the electro-dynamic loudspeaker isattached directly to the diaphragm. Because the conductor is placeddirectly onto the thin diaphragm, the conductor should be constructed ofa material having a low mass and should also be securely attached to thefilm at high power (large current) and high temperatures.

[0009] The frame of the electro-dynamic loudspeaker supports themagnets, the diaphragm, and the terminal. The frame presents its owndesign challenges. The frame must be capable of being bonded to thediaphragm film. The frame must be rigid enough to maintain the diaphragmfilm in uniform tension and not be susceptible to deforming duringhandling, assembly, or over time. A ferrous frame has the advantage ofbeing capable of carrying magnetic energy or flux. The frame also shouldbe capable of withstanding high environmental temperatures, humidity,salt spray, etc.

[0010] Alternatively, a plastic frame has an advantage in that theunderlying process and mold tooling can be designed with spring loadedinserts to provide very precise control of the separation distancebetween the top of the imbedded magnets and the film conductor. Thiscontrol is effective even for magnet lots with relatively high thicknessvariation. Such improved control allows wide tolerance and more economicmagnet specifications. In addition, because separation distancevariation is reduced, and process to design capability is improved,performance may be improved by reducing and minimizing the meanseparation distance between driver and magnets. Finally, the plasticframe molding process readily and economically accepts variousadditional and beneficial features such as locators and mounting tabsthat can be incorporated into the part at little added cost. Thiscapability improves application value.

[0011] Accordingly, designing conductors for electro-dynamic loudspeakerapplications presents various challenges such as selecting the speakerwith the desired audible output for a given location that will fitwithin the size and location constraints of the desired applicationsenvironment. Electro-dynamic loudspeakers exhibit a defined acousticaldirectivity pattern relative to each speaker's physical shape and thefrequency of the audible output produced by each loudspeaker.Consequently, when an audio system is designed, loudspeakers possessinga desired directivity pattern over a given frequency range are selectedto achieve the intended performance of the system. Different loudspeakerdirectivity patterns may be desirable for various loudspeakerapplications. For example, for use in a consumer audio system for a homelistening environment, a wide directivity may be preferred. In theapplication of a loudspeaker, a narrow directivity may be desirable todirect sound, e.g., voice, in a predetermined direction.

[0012] Often, space limitations in the listening environment prohibitthe use of a loudspeaker in an audio system that possesses the preferreddirectivity pattern for the system's design. For example, the amount ofspace and the particular locations available in a listening environmentfor locating and/or mounting the loudspeakers of the audio system mayprohibit the use of a particular loudspeaker that exhibits the intendeddirectivity pattern. Also, due to space and location constraints, it maynot be possible to position or oriented the desired loudspeaker in amanner consistent with the loudspeaker's directivity pattern.Consequently, size and space constraints of a particular environment maymake it difficult to achieve the desired performance from the audiosystem. An example of a listening environment having such constraints isthe interior passenger compartment of an automobile or other vehicle.

[0013] While the electric circuitry of electro-dynamic loudspeakers maypresent design challenges, electro-dynamic loudspeakers are verydesirable loudspeakers because they are designed to have a very shallowdepth. With this dimensional flexibility, electro-dynamic loudspeakersmay be positioned at locations where conventional loudspeakers would nottraditionally fit. This dimensional flexibility is particularlyadvantageous in automotive applications where positioning a loudspeakerat a location that a conventional loudspeaker would not otherwise fitcould offer various advantages. Further, because the final loudspeakerassembly may be mounted on a vehicle, it is important that the assemblybe rigid during shipping and handling so that the diaphragm or framedoes not deform during installation.

[0014] While conventional electro-dynamic loudspeakers are shallow indepth and may therefore be preferred over conventional loudspeakers foruse in environments requiring thin loudspeakers, electro-dynamicloudspeakers have a generally rectangular planar radiator that isgenerally relatively large in height and width to achieve acceptableoperating wavelength sensitivity, power handling, maximum sound pressurelevel capability and low-frequency bandwidth. Unfortunately, the largerectangular size results in a high-frequency beam width angle orcoverage that may be too narrow for its intended application. Thehigh-frequency horizontal and vertical coverage of a rectangular planarradiator is directly related to its width and height in an inverserelationship. As such, large radiator dimensions exhibit narrowhigh-frequency coverage and vice versa.

SUMMARY

[0015] The invention provides several frame structures and methods forconstructing frames related to electro-dynamic loudspeakers. Theelectro-dynamic loudspeakers include a frame, a plurality of magnets anda diaphragm. The frame may be molded from plastic to include the magnetsmolded into the frame. The magnets may be embedded into the frame duringthe frame molding process.

[0016] Embedding the magnets in the frame may involve placing themagnets in an injection mold and injecting molten resin around themagnets to partially encapsulate the magnets within the resin. Themagnets may include a first magnet embedded in the frame in a first rowand a second magnet embedded in the frame in a second row. Each of thefirst and second rows may include a plurality of longitudinallyextending magnets. The magnets may be positioned end-to-end in aplurality of rows. Magnets may be positioned in the first row withpolarity that is opposite to the polarity of the magnets positioned inthe second row. Each of the magnets may include a first surface that iscoplanar with an inner surface of the frame and a second surface of themagnets that extends into the frame towards an outer surface of theframe.

[0017] The diaphragm may be mounted to the frame a determined distancefrom the magnets. Magnetic fields produced between the rows of magnetsmay interact with a magnetic field produced with electrical signalsprovided on a conductor coupled with the diaphragm. The diaphragm mayinclude a thin film. The film may be movable in response to theinteraction between the magnetic fields produced by the magnets and themagnetic field produced with the electrical signals. The resultingmovement of the film may produce sound.

[0018] Other systems, methods, features and advantages of the inventionwill be or will become apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention can be better understood with reference to thefollowing drawings and description. The components in the figures arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like reference numerals designate corresponding parts throughout thedifferent views.

[0020]FIG. 1 is a perspective view of an electro-dynamic loudspeaker asit would appear with the grille removed.

[0021]FIG. 2 is an exploded perspective view of the electro-dynamicloudspeaker shown in FIG. 1 having a grille.

[0022]FIG. 3 is a cross-sectional view of the electro-dynamicloudspeaker taken along line 3-3 of FIG. 1.

[0023]FIG. 4 is an enlarged cross-sectional view of the encircled areaof FIG. 3.

[0024]FIG. 5 is a plan view of a film included in the electro-dynamicloudspeaker of FIG. 1.

[0025]FIG. 6 is a plan view of an example vacuum platen for use inconstructing the electro-dynamic loudspeaker of FIG. 1.

[0026]FIG. 7 is a cross-sectional side view of the vacuum platen shownin FIG. 6.

[0027]FIG. 8 is a perspective view of an example clamp assembly for usein constructing the electro-dynamic loudspeaker of FIG. 1.

[0028]FIG. 9 is a cross-sectional side view of the clamp assembly ofFIG. 8.

[0029]FIG. 10 is a plan view of the clamp assembly of FIG. 8 in a closedposition.

[0030]FIG. 11 is a cross-sectional side view of the clamp assembly ofFIG. 8 in the closed position.

[0031]FIG. 12 is a plan view of an example assembly fixture with a frameof the electro-dynamic loudspeaker of FIG. 1 positioned on the assemblyfixture.

[0032]FIG. 13 is a cross-sectional side view of the assembly fixture andframe illustrated in FIG. 12.

[0033]FIG. 14 is a plan view of the clamp assembly of FIG. 8 positionedon top of the assembly fixture of FIG. 12.

[0034]FIG. 15 is a cross-sectional side view of the closed clampassembly of FIGS. 10 and 11 positioned on top of the assembly fixture ofFIG. 12.

[0035]FIG. 16 is cross-sectional side view of an example work-in-processpartially constructed electro-dynamic loudspeaker.

[0036]FIG. 17 is a cross-sectional side view of an example finishedelectro-dynamic loudspeaker.

[0037]FIG. 18 is a cross-sectional view of an example film tensioningdevice.

[0038]FIG. 19 is a cross-sectional side view of another example filmtensioning device.

[0039]FIG. 20 is a perspective view of yet another example filmtensioning device.

[0040]FIG. 21 is a cross-sectional side view depicting use of thealternate tensioning member shown in FIG. 20.

[0041]FIG. 22 is a cross-sectional side view further depicting diaphragmtensioning using the tensioning device shown in FIG. 20.

[0042]FIG. 23 depicts an example frame in an undeformed state and adeformed state.

[0043]FIG. 24 is an exploded perspective view of another exampleloudspeaker.

[0044]FIG. 25 is a cross sectional view of an injection mold used toconstruct an example bowed frame of the loudspeaker depicted in FIG. 24.

[0045]FIG. 26 is a perspective bottom view of an example plastic frameof a loudspeaker.

[0046]FIG. 27 is a perspective top view of the frame illustrated in FIG.26.

[0047]FIG. 28 is a cross-sectional view of the frame illustrated in FIG.27 taken along line 28-28.

[0048]FIG. 29 is an enlarged partial cross-sectional view of an examplemagnet assembly and the plastic frame depicted in FIG. 26.

[0049]FIG. 30 is a partial perspective view of a terminal detail of anexample plastic frame and an example magnet assembly.

[0050]FIG. 31 is an exploded perspective view of another exampleelectro-dynamic loudspeaker.

[0051]FIG. 32 is a cross-sectional view of a casement and a diaphragmsubassembly taken along line 32-32 of the electro-dynamic loudspeaker ofFIG. 31.

[0052]FIG. 33 is a cross-sectional view of the electro-dynamicloudspeaker of FIG. 31.

[0053]FIG. 34 is a cross-sectional view of an injection mold.

[0054]FIG. 35 is a cross-sectional view of another exampleelectro-dynamic loudspeaker that includes a retainer coupling a casementto a frame.

[0055]FIG. 36 is an exploded cross-sectional view of yet another exampleelectro-dynamic loudspeaker.

[0056]FIG. 37 is a partial perspective view of the electro-dynamicloudspeaker depicted in FIG. 36.

[0057]FIG. 38 is a partial cross-sectional view of an alternateinjection mold incorporating a film tensioning feature in the mold tool.

[0058]FIG. 39 is a cross-sectional view of another example loudspeaker.

[0059]FIG. 40 is a cross-sectional view of still another exampleelectro-dynamic loudspeaker.

[0060]FIG. 41 is a flow diagram depicting a method of constructing anelectro-dynamic loudspeaker.

DETAILED DESCRIPTION

[0061]FIG. 1 is a perspective view of an electro-dynamic loudspeaker 100of the invention. As shown in FIG. 1, the electro-dynamic loudspeaker isa generally planar loudspeaker having a frame 102 with a diaphragm 104attached in tension to the frame 102. A conductor 106 is positioned onthe diaphragm 104. The conductor 106 is shaped in serpentine fashionhaving a plurality of substantially linear sections (or traces) 108longitudinally extending along the diaphragm interconnected by radii 110to form a single current path. Permanent magnets 202 (shown in FIG. 2)are positioned on the frame 102 underneath the diaphragm 104, creating amagnetic field.

[0062] Linear sections 108 are positioned within the flux fieldsgenerated by permanent magnets 202. The linear sections 108 carrycurrent in a first direction 112 and are positioned within magnetic fluxfields having similar directional polarization. Linear sections 108 ofconductor 106 having current flowing in a second direction 114, that isopposite the first direction 112, are placed within magnetic flux fieldshaving an opposite directional polarization. Positioning the linearsections 108 in this manner assures that a driving force is generated bythe interaction between the magnetic fields developed by magnets 202 andthe magnetic fields developed by current flowing in conductor 106. Assuch, an electrical input signal traveling through the conductor 106causes the diaphragm 104 to move, thereby producing an acousticaloutput.

[0063]FIG. 2 is an exploded perspective view of the electro-dynamicloudspeaker 100 shown in FIG. 1. As illustrated in FIG. 2, the flatpanel loudspeaker 100 includes a frame 102, a plurality of high energymagnets 202, a diaphragm 104, an acoustical dampener 236 and a grille228. Frame 102 provides a structure for fixing magnets 202 in apredetermined relationship to one another. In the depicted embodiment,magnets 202 are positioned to define five rows of magnets 202 with threemagnets 202 in each row. The rows are arranged with alternating polaritysuch that fields of magnetic flux are created between each row. Once theflux fields have been defined, diaphragm 104 is fixed to frame 102 alongits periphery.

[0064] A conductor 106 is coupled to the diaphragm 104. The conductor106 is generally formed as an aluminum foil bonded to the diaphragm 104.The conductor 106 can, however, be formed from other conductivematerials. The conductor 106 has a first end 204 and a second end 206positioned adjacent to one another at one end of the diaphragm 104.

[0065] As shown in FIG. 2, frame 102 is a generally dish-shaped memberpreferably constructed from a substantially planar contiguous steelsheet. The frame 102 includes a base plate 208 surrounded by a wall 210.The wall 210 terminates at a radially extending flange 212. The frame102 further includes apertures 214 and 216 extending through flange 212to provide clearance and mounting provisions for a conductor assembly230.

[0066] Conductor assembly 230 includes a terminal board 218, a firstterminal 220 and a second terminal 222. Terminal board 218 includes amounting aperture 224 and is preferably constructed from an electricallyinsulating material such as plastic, fiberglass or other insulatingmaterial. A pair of rivets or other connectors (not shown) pass throughapertures 214 to electrically couple first terminal 220 to first end 204and second terminal 222 to second end 206 of conductor 106. A fastenersuch as a rivet 226 extends through apertures 224 and 216 to coupleconductor assembly 230 to frame 102.

[0067] A grille 228 functions to protect diaphragm 104 from contact withobjects inside the listening environment while also providing a methodfor mounting loudspeaker 100. The grille 228 has a substantially planarbody 238 having a plurality of apertures 232 extending through thecentral portion of the planar body 238. A rim 234 extends downward,substantially orthogonally from body 238, along its perimeter and isdesigned to engage the frame 102 to couple the grille 228 to the frame102.

[0068] An acoustical dampener 236 is mounted on the underside of thebase plate 208 of the frame 102. Dampener 236 serves to dissipateacoustical energy generated by diaphragm 104 thereby minimizingundesirable amplitude peaks during operation. The dampener 236 may bemade of felt, or a similar gas permeable material.

[0069]FIG. 3 is a cross-sectional view of the electro-dynamicloudspeaker taken along line 3-3 of FIG. 1. FIG. 3 shows the frame 102having the diaphragm 104 attached in tension to the frame 102 and thepermanent magnets 202 positioned on the frame 102 underneath thediaphragm 104. Linear sections 108 of the conductor 106 are also shownpositioned on top of the diaphragm 104.

[0070]FIG. 4 is an enlarged cross-sectional view of the encircled areaof FIG. 3. As illustrated by FIG. 4, the diaphragm 104 is comprised of athin film 400 having a first side 402 and a second side 404. First side402 is coupled to frame 102. Generally, the diaphragm 104 is secured tothe frame 102 by an adhesive 406 that is curable by exposure toradiation. However, the diaphragm 104 may secured to the frame 102 byother mechanism, such as those known in the art.

[0071] To provide a movable membrane capable of producing sound, thediaphragm 104 is mounted to the frame in a state of tension and spacedapart a predetermined distance from magnets 202. The magnitude oftension of the diaphragm 104 depends on the speaker's physicaldimensions, materials used to construct the diaphragm 104 and thestrength of the magnetic field generated by magnets 202. Magnets 202 aregenerally constructed from a highly energizable material such asneodymium iron boron (NdFeB), but may be made of other magneticmaterials. The thin diaphragm film 400 is generally apolyethylenenaphthalate sheet having a thickness of approximately 0.001inches; however, the diaphragm film 400 may be formed from materialssuch as polyester (e.g., known by the tradename “Mylar”), polyamide(e.g., known by the tradename “Kapton”) and polycarbonate (e.g., knownby the tradename “Lexan”), and other materials known by those skilled inthe art for forming diaphragms 104.

[0072] The conductor 106 is coupled to the second side 404 of thediaphragm film 400. The conductor 106 is generally formed as an aluminumfoil bonded to diaphragm film 400, but may be formed of other conductivematerial known by those skilled in the art.

[0073] The frame 102 includes a base plate 208 surrounded by a wall 210extending generally orthogonally upward from the plate 208. The wall 210terminates at a radially extending flange 212 that defines asubstantially planar mounting surface 414. A lip 416 extends downwardlyfrom flange 212 in a direction substantially parallel to wall 210. Baseplate 208 includes a first surface 418, a second surface 420 and aplurality of apertures 422 extending through the base plate 208. Theapertures 422 are positioned and sized to provide air passagewaysbetween the first side 402 of diaphragm 104 and first surface 418 offrame 102. An acoustical dampener 236 is mounted to second surface 420of frame base plate 208.

[0074] Various systems for assembling an example loudspeaker 100 willnow be described. A first example system is depicted in FIGS. 5-17. Thefirst system includes a vacuum platen 600 (FIGS. 6-7) and a film clamp800 (FIGS. 8-9). Vacuum platen 600 and film clamp 800 may be used inconjunction with one another to restrain diaphragm 104 (FIG. 5) in aflat position without tension. Once diaphragm 104 is fixed within clamp800, film 400 may be subsequently tensioned as will be described later.

[0075] The initial flattening and clamping of diaphragm 104 may providethe assembler with a known diaphragm state to which tension may beadded. Difficulties may arise in attempting to obtain a reproducibletension during subsequent assembly operations when diaphragm 104 is notfirst placed in a substantially flat, no tension state. This firstexample system includes vacuum platen 600 and film clamp 800 to achievea repeatable diaphragm state. In other examples, any other mechanism(s)and/or techniques capable of providing a known diaphragm state to whichtension may be added may be used.

[0076] The example vacuum platen 600 includes a base 700 having a body702 and a pedestal 704 protruding from a first surface 602 of body 702.Pedestal 704 includes an upper surface 706 positioned substantiallyparallel to first surface 602. A vacuum passageway 708 may extendthrough pedestal 704 and body 702 to couple upper surface 706 with avacuum source 604. A cap 710 may be coupled to pedestal 704 along uppersurface 706. Cap 710 may be constructed from a gas permeable materialsuch as porous aluminum. Base 700 may be constructed from a gasimpermeable material. Accordingly, a suction force is created along anupper surface 606 of cap 710 when vacuum source 604 draws a vacuum invacuum passageway 708.

[0077] The example film clamp 800 includes an upper clamp half 802 and alower clamp half 804 connected by a hinge 806. The illustrated upperclamp half 802 includes a generally rectangularly shaped body 808 and anelastomeric gasket 810. Body 808 includes an aperture 900 (FIG. 9)extending through body 808. Elastomeric gasket 810 includes a similarlyshaped aperture 902 (FIG. 9) extending through the thickness of gasket810. Elastomeric gasket 810 may be attached to body 808 to provide acompressible high friction surface 812 for engagement with diaphragm104.

[0078] The illustrated lower clamp half 804 is constructed from agenerally rectangularly shaped aluminum frame 814 having an aperture 904extending through the lower clamp half 804. Lower clamp half 804includes an upper surface 906 and a lower surface 908.

[0079] During the loudspeaker assembly process, film clamp 800 may bepositioned on vacuum platen 600 such that pedestal 704 enters aperture904 of lower clamp half 804 as illustrated in FIG. 9. Once seated, uppersurface 906 of lower clamp half 804 may be substantially coplanar withupper surface 606 of cap 710. In order to properly position diaphragm104, upper clamp half 802 may be rotated to place film clamp 800 in theopen position depicted in FIG. 8.

[0080] With vacuum source 604 turned off, diaphragm 104 may be placed onupper surface 606. Diaphragm 104 may be aligned relative to lower clamphalf 804 using sights 816. Sights 816 may be visual markings, rods,rings, notches or any other form of alignment mechanism formed ondiaphragm 104 to assist in the alignment procedure. The location ofsights 816 effectively defines a perimeter portion 818 and a centerportion 820 of diaphragm 104. Center portion 820 may contain most, ifnot all, of the material which will remain coupled to frame 102 at thecompletion of the assembly process.

[0081] Once diaphragm 104 has been properly positioned, vacuum may besupplied to cap 710 via vacuum source 604. Because cap 710 isconstructed from a gas permeable material, diaphragm 104 is forced toclosely conform to planar upper surface 606. While the vacuum source ismaintained, upper clamp half 802 may be rotated to place film clamp 800in a closed position as shown in FIGS. 10 and 11. During clamp closure,elastomeric gasket 810 may deform locally to account for the thicknessof diaphragm 104. Latches 822 secure upper clamp half 802 to lower clamphalf 804. It should be appreciated that latches 822 are merely exemplarydevices for coupling the clamp halves together and that any number offastening devices may be implemented. Once upper clamp half 802 isclamped to lower clamp half 804, vacuum is turned off and film clamp 800holding diaphragm 104 in an untensioned state is removed from vacuumplaten 600.

[0082] Frame 102 may be fixtured in an example assembly fixture 1200(FIGS. 12 and 13). Assembly fixture 1200 may be shaped substantiallysimilarly to vacuum platen 600. However, assembly fixture 1200 mayinclude a recess 1300 for receipt of a portion of frame 102. Assemblyfixture 1200 includes a gage surface 1302 offset a predetermineddistance 1304 from planar mounting surface 408 of frame 102. In order toapply tension to diaphragm 104, distance 1304 is greater than thethickness of lower clamp half 804. The magnitude of tension generated isoptimized by defining distance 1304 in concert with the physicalcharacteristics of frame 102 and diaphragm 104.

[0083] Diaphragm 104 may be mechanically coupled with frame 102. Forexample, adhesive 406 may be applied to planar mounting surface 408 offrame 102. Adhesive 406 may alternatively be applied to diaphragm 104.After application of adhesive 406, film clamp 800 including clampeddiaphragm 104 may be positioned on assembly fixture 1200 such that frame102 enters aperture 904 of lower clamp half 804 (FIGS. 14 and 15). Thediaphragm 104 may contact adhesive 406 and planar mounting surface 408of frame 102. Contact may occur prior to lower surface 908 of lowerclamp half 804 contacting gage surface 1302 of assembly fixture 1200. Toproduce the desired tension in film 400, film clamp 800 is forced downover assembly fixture 1200 so that lower surface 908 engages gagesurface 1302.

[0084] Depending on the type of adhesive used, a subsequent process maybe required. For example, adhesive 406 is curable by exposure toradiation. Accordingly, while film clamp 800 is coupled to assemblyfixture 1200, a radiation source 1500 is energized to cure the adhesiveand secure diaphragm 104 to frame 102. Alternatively, where some othermechanical coupling mechanism is used, appropriate processes may need tobe performed.

[0085] A second example system used to tension the diaphragm of aloudspeaker 100 is described with reference to FIGS. 16 and 17. In thissystem, frame 102 includes an elongated radially extending flange 1600which does not include a downwardly extending lip. The remaining planarloudspeaker components are substantially similar to those previouslydescribed. The assembly process may include positioning diaphragm 104 ina substantially flat, no tension state as previously described. However,it should be appreciated that the flattening and clamping steps are notnecessarily required to construct planar loudspeaker according to thissystem. Similarly, alternate tensioning methods that are described arenot intended to be limited to include the flattening and clampingprocess.

[0086] A bead of adhesive 406 may be applied along the periphery ofeither or both frame 102 and diaphragm 104. Diaphragm 104 may then bealigned with and bonded to frame 102 via adhesive 406. As noted earlier,adhesive 406 may be a light curable material or any other suitablebonding agent which may affix the dissimilar materials to one another.Similarly, adhesive 406 may any other coupling mechanism to mechanicallycouple the diaphragm 104 to the frame 102.

[0087] Radially extending flange 1600 may be mechanically deformed bybending an outer peripheral region down from line 1700 as shown in FIG.17 to tension diaphragm 104. Line 1700 acts as a fulcrum around theperimeter of frame 102 about which diaphragm 104 is stretched. Theproper diaphragm tension may be obtained in a variety of ways. Forexample, if diaphragm 104 was initially coupled to frame 102 in asubstantially flat, non-tension state, a deflection distance 1702 may beempirically determined by testing. Once the proper deflection distanceis determined, hard tooling may be created to repeatably deform frame102 and move radially extending flange 1600 the predetermined deflectiondistance 1702 during the assembly of each loudspeaker 100.

[0088] Another example system of assuring proper film tension includes afeedback system 1602. One example feedback system may involve placing aknown load at the center of diaphragm 104 and measuring the deflectionof the diaphragm at the load application point. The desired deflectionper load may be empirically determined by testing where the resonancefrequency of diaphragm 104 is plotted against deflection per a givenload. Once the desired resonance frequency is determined for a givenspeaker geometry, a target diaphragm deflection per given load may bedetermined. The feedback system may operate by measuring the actualdiaphragm deflection at a known load with a deflection sensor 1604. Themeasured actual deflection may be compared to the target deflection.

[0089] Frame 102 may be deformed until the measured deflection issubstantially equal to the target deflection, thereby properlytensioning diaphragm 104 to produce the desired resonance frequency.Logic control systems such as proportional, integral, derivative closedfeedback loops, etc. may be implemented to control the mechanicaldeflection of frame 102 during the tensioning process. Such a controlsystem may provide a high degree of repeatability regarding filmtensioning.

[0090] Another example feedback system 1704 may directly measureresonance frequency during film tensioning using a frequency sensor1706. In this control scheme, diaphragm 104 may be repeatedly excitedand the resonance frequency measured. The measured frequency may becompared to a desired target frequency during film tensioning. Frame 102may be deformed until the measured resonance frequency matches thetarget frequency within an acceptable tolerance. It should beappreciated that the feedback systems described may be used with any ofthe tensioning techniques described.

[0091] Yet another film tensioning system will be described in greaterdetail with reference to FIG. 18. An example film tensioner 1800includes an upper plate 1802 and a lower plate 1804. Plates 1802 and1804 have matching beveled apertures 1806 and 1808, respectively. Centerportion 820 of diaphragm 104 is positioned within the openings definedby apertures 1806 and 1808. Apertures 1806 and 1808 may be sized andshaped slightly larger than frame 102 to allow insertion of frame 102within one of the apertures 1806 and 1808.

[0092] Upper plate 1802 may include an annular groove 1810 having anasymmetrical cross-section as shown in FIG. 18. Lower plate 1804 mayinclude an annular groove 1812 shaped as the mirror image of groove1810. A first elastomeric member 1814 may be positioned within groove1810 and a second elastomeric member 1816 may be positioned withingroove 1812. Grooves 1810 and 1812 may be shaped to constrain movementof the elastomeric members 1814 and 1816 toward apertures 1806 and 1808,respectively. In addition, grooves 1810 and 1812 may be shaped to allowmovement of elastomeric members 1814 and 1816 away from apertures 1806and 1808. Specifically, the annular grooves 1810 and 1812 may be shapedto impart a lateral force to center portion 820 of diaphragm 104 when anaxial force is applied to upper plate 1802 and lower plate 1804 drawingthem toward one another.

[0093] Upper plate 1802 may also include threaded apertures 1818.Stepped apertures 1820 extend through lower plate 1804. Threadedfasteners 1822, which are illustrated as bolts, may be inserted inapertures 1820 and tightened into threaded apertures 1818 to draw upperplate 1802 and lower plate 1804 together. It should be appreciated thatupper plate 1802 and lower plate 1804 may be drawn together using avariety of mechanisms such as toggle clamps, jack screws, hydrauliccylinders or any other known clamping and force producing devices.

[0094] In this example technique, the film may first be tensioned bydrawing upper plate 1802 and lower plate 1804 together. Adhesive 406 (orsome other coupling mechanism) may be placed on the tensioned portion ofdiaphragm 104 and/or planar mounting surface 408 of frame 102. Whileupper plate 1802 is clamped to lower plate 1804, frame 102 may be placedinto contact with diaphragm 104. Once the adhesive has cured (ormechanical coupling completed), the threaded fasteners 1822 may beremoved and upper plate 1802 may be separated from lower plate 1804. Itshould also be appreciated that apertures 1806 and 1808 may be sized toallow entry of light waves to cure adhesive 406, or to allowmanipulation of some other coupling mechanism, if so desired. Dependingon the specific configuration of the loudspeaker 100, perimeter portion818 of diaphragm 104 may be trimmed to remove any film extending beyondlip 306.

[0095] With reference to FIG. 19, another example film tensioningtechnique is depicted. The fixturing used to practice this exampletechnique includes a fixture 1900 having a lower die 1902, and an upperdie 1904. Fixture 1900 may function to restrain the periphery ofdiaphragm 104 and define a cavity 1906 between one side of the diaphragm104 and lower die 1902. A fluid source 1908 may supply pressurized fluidto cavity 1906. Because lower die 1902 is constructed from asubstantially rigid material, diaphragm 104 may elongate in tension asdepicted in FIG. 19. Pressure is maintained within cavity 1906 whileframe 102 is mechanically coupled with diaphragm 104. Diaphragm 104 maybe secured to frame 102 using any number of previously discussed bondingtechniques including mechanical fasteners, radiation curable adhesives,multi-part epoxies, heat curable adhesives or pressure sensitivecompounds.

[0096] After diaphragm 104 has been fixed to frame 102, upper die 1904may be removed. If desired, excess diaphragm material extending beyondthe perimeter of frame 102 may be removed.

[0097] In this example technique, some of the initial tension generatedby the pressurized fluid may relax during subsequent frame attachmentprocess. Accordingly, a tension greater than the final desired tensionmay be initially induced via fluid source 1908 to assure that the filmis properly tensioned during use.

[0098] FIGS. 20-22 depict another example of fixturing used to tensiondiaphragm 104 prior to attaching diaphragm 104 to frame 102. An examplespider 2000 may operate in conjunction with an example base plate 2100to tension diaphragm 104. Spider 2000 may be placed on a first side ofdiaphragm 104 while base plate 2100 may be placed on the opposite sideof the diaphragm 104. Spider 2000 may function by converting an axialforce applied in direction 2102 to a lateral tension produced in opposeddirections 2200.

[0099] The illustrated spider 2000 is a generally pyramidal memberhaving a hub 2002 positioned proximate to a truncated portion of thepyramid. A plurality of legs 2004 angularly extend from hub 2002. Eachof the legs 2004 include a body portion 2006 and a foot portion 2008.Each foot portion 2008 radially extends from the distal end of each leg2004. A pad 2010 is coupled (as shown in FIG. 20) to a lower surface ofeach foot 2008. Pads 2010 may be constructed from a high friction,elastomeric material that is suitable for gripping diaphragm 104 withoutcausing damage to diaphragm 104.

[0100] The illustrated base plate 2100 is a generallyrectangularly-shaped member having an aperture 2104 extending throughthe base plate 2100. Aperture 2104 may be shaped similarly to theperimeter of frame 102 and sized such that frame 102 may be insertedinto aperture 2104. Base plate 2100 includes a low friction surface 2106upon which diaphragm 104 may freely slide. As best shown in FIG. 21,each pad 2010 is supported by a portion of base plate 2100.

[0101] During tensioning, diaphragm 104 may be placed between base plate2100 and spider 2000. An axial force may be applied to spider 2000 indirection 2102. Due to the angular orientation of legs 2004 relative tolow friction surface 2106, at least some of the axial force applied indirection 2102 may be converted to opposing forces in opposed directions2200. The opposed forces may tension diaphragm 104. After tensioning,frame 102 is mechanically coupled to diaphragm 104 as previouslydiscussed.

[0102]FIG. 23, is yet another example system for loudspeaker 100assembly. In this system, frame 102 may be elastically deformed prior toattachment of diaphragm 104. The deformed frame 102 is represented inphantom lines at reference numeral 2300. It should be appreciated thatany number of force generating devices or tools such as jack screws,hydraulic rams or other force producing devices may be used toelastically deform frame 102 by inwardly deflecting radially extendingflange 304 and lip 306 (FIG. 3) of frame 102. Frame 102 may bemaintained in the deformed state shown as 2300 while diaphragm 104(FIG. 1) is attached to planar mounting surface 408 (FIG. 4).

[0103] Once diaphragm 104 has been securely attached to frame 102, theexternal forces deforming frame 102 may be released. Because frame 102was elastically deformed, flange 304 and lip 306 have a tendency tospring-back to their originally undeformed state. This tendency isresisted by diaphragm 104. Diaphragm 104 elongates as the deformed frameattempts to return to its undeformed state until an equilibrium isreached. Frame 102 may be constructed from steel, aluminum or any numberof composite materials capable of being deformed. Materials having amodulus of elasticity less than 29,000 KSI are contemplated to provide arelatively large elastic deformation prior to yield. A large framedeformation is beneficial to account for elongation or deformation ofadhesive 406 or other mechanical coupling used to bond diaphragm 104 toframe 102.

[0104] Frames constructed from molded plastic or composite materialsoffer additional opportunities to incorporate an arc or a bow across aframe as depicted in FIG. 24. In illustrated example, a loudspeaker 2400includes a bowed frame 2402. Frame 2402 may function as a spring washerto tension diaphragm 104.

[0105] During assembly of loudspeaker 2400, frame 2402 may be forced toa substantially planar condition. Diaphragm 104 may be coupled to frame2402 while frame 2402 is in the substantially flat planar condition.Once diaphragm 104 has been securely attached to frame 2402, theexternal force maintaining frame 2402 in a substantially flat planarcondition may be released. Because frame 2402 is elastically deformed,the frame has a tendency to return to the bowed shape. This tendency isresisted by diaphragm 104. Diaphragm 104 may elongate as frame 2402attempts to return to the originally bowed shape until an equilibrium isreached. At equilibrium, diaphragm 104 is in a tensioned state and nofurther movement of diaphragm 104 and/or frame 2402 occurs.

[0106] The bowed frame 2402 may be created using injection moldingequipment such as that shown in FIG. 25. An example injection mold 2500includes an upper mold half 2502 and a lower mold half 2504. A partingline 2506 runs along the length of frame 2402. The position of partingline 2506 is defined by the interface position of upper mold half 2502and lower mold half 2504. The arc or bow may be created by imparting atemperature differential between first mold half 2502 and second moldhalf 2504. The use of a differential mold temperature to bow the frame2402 will conceptually work for all molding resins. However,semi-crystalline resins such as Polybutylene Terephthalate (PBT),Polyethylene Terephthalate (PET), nylons, Polypropylene (PP) and blendsincorporating these materials will produce an especially pronounced bow.

[0107] Alternatively, bowed frame 2402 may be produced from a moldhaving curved cavity surfaces. Standard temperature control techniquesmay then be used. In another alternative, both concepts may be used incombination. Specifically, a mold having curved surfaces may becontrolled to maintain mold half temperature differentials and obtainthe desired bowed frame 2402.

[0108] With reference to FIGS. 26 and 27, another example frame 2600 isshown. FIG. 26 depicts the bottom of frame 2600 while FIG. 27 shows thetop of frame 2600. Frame 2600 may be constructed from a reinforcedplastic or other similar material. The illustrated frame 2600 is agenerally dish-shaped member having a base 2602 surrounded by a wall2604 extending substantially orthogonally from the base 2602. Wall 2604terminates at a radially extending flange 2606 which defines asubstantially planar mounting surface 2700. During assembly, diaphragm104 (FIG. 1) is coupled to frame 2600 along planar mounting surface2700. Base 2602 includes a first surface 2702, a second surface 2608 anda plurality of apertures 2610 extending through the base 2602. Apertures2610 are positioned and sized to provide the desired passageways for airpositioned between first surface 2702 and diaphragm 104 to flow.

[0109] A plurality of magnets 2704 may be integrally molded within frame2600. As best shown in FIG. 28, each of magnets 2704 may include a slot2800 extending transversely across each end of magnet 2704. FIG. 29depicts an example of slots 2800 filled with the composite material offrame 2600 after an over-molding process has been completed.Accordingly, slots 2800 may perform a retention function to fix each ofmagnets 2704 within frame 2600. Each magnet 2704 may include an uppersurface 2802 positioned coplanar with surface 2702 of frame 2600.Because magnets 2704 are recessed within base 2602, the overall heightof frame 2600 may be reduced to provide a low-profile frame andloudspeaker assembly.

[0110] Additionally, the embedded magnet design may provide economicbenefits related to magnets 2704. Magnets mounted to a steel frame haveclosely controlled thicknesses to assure that the upper surface of eachmagnet is positioned at a proper distance from diaphragm 104. Aspreviously discussed, surfaces 2802 of magnets 2704 are designed to besubstantially co-planar with surface 2702 of frame 2600.

[0111] During molding, the magnets 2704 may be placed on a spring loadedtool 2900 (shown in phantom line in FIG. 29) to align each upper surface2802 of magnets 2704 with each other in substantially a single plane.The magnets 2704 are placed substantially in a single plane to generallymaintain a uniform distance from the diaphragm 104 (FIG. 1). Becauseinjected resin may flow around the magnets 2704 and the spring loadedtool, the thicknesses of magnets 2704 need not be closely controlled.For example, FIG. 29 depicts a first magnet 2704 having a firstthickness 2902. A second magnet 2904 has a different thickness 2906. Thevariation in magnet thickness is accommodated within the body of frame2600. A cost savings results by using magnets having a greater toleranceon the thickness dimension.

[0112] As best shown in FIG. 26, a pair of example electrical terminals2612 may be over-molded within frame 2600. Accordingly, electricalterminals 2612 are partially embedded within frame 2600. Each electricalterminal 2612 includes a male prong portion 2614 and an end portion2616. An intermediate portion positioned between male prong portion 2614and end portion 2616 is embedded within frame 2600. Male prong portion2614 may extend away from the body of frame 2600. A socket 2618 may beintegrally molded with frame 2600. Socket 2618 includes a wall 2620extending from surface 2608. Wall 2620 may surround male prong portions2614 and may be shaped to mate with a female plug (not shown). Thefemale plug may be used to electrically couple the loudspeaker 100 to apower source.

[0113] Each end portion 2616 may include an aperture 2622 extendingthrough the end portion 2616. Apertures 2622 may also extend throughflange 2606. After diaphragm 104 is coupled to mounting surface 2700, anelectrical connection may be made between end portions 2616 andconductor 106 of diaphragm 104 by coupling electrically conductingjumpers or fasteners (not shown) to end portions 2616 and conductor 106.

[0114] With reference to FIG. 30, another example frame 3000 isdepicted. Frame 3000 includes an example pair of electrical terminals3002 molded within an example frame 3004. Each electrical terminal 3002includes male prong portions 3006, intermediate portions 3007 and endportions 3008. Intermediate portion 3007 is embedded within frame 3000between male prong portions 3006 and end portion 3008. Inwardlyextending end portions 3008 may be electrically coupled with conductor106 of diaphragm 104 after diaphragm 104 has been coupled to frame 3004.Electrical coupling may be by soldering, connectors, frictional contactor any other mechanism for electrically connecting electrical terminals3002 with conductor 106.

[0115] To construct the example frames 2600 and 3000 having theintegrally molded metallic components as previously discussed withreference to FIGS. 26, 27 and 30, an over-molding technique may be used.FIG. 41 depicts the process of constructing an electro-dynamicloudspeaker having a frame similar to frame 2600 or frame 3000. Magnets2704 and electrical terminals 2612 may first be placed within an openinjection mold cavity at step 4102. Magnets 2704 and electricalterminals 2612 may be positioned within the mold to assure that moltenplastic resin covers at least a portion of each metallic component toretain each metallic component within frame 2600. The injection mold mayalso include features to mask off portions of the metallic components soselected portions are not contacted by molten plastic resin. The mold isclosed at step 4104. Molten resin may be injected to fill the cavityduring step 4106. Upon completion of this process, the resin issolidified at step 4108 and magnets 2704 and electrical terminals 2612are fixed within frame 2600. Magnets 2704 and electrical terminals 2612include exposed surfaces for the purpose previously described.

[0116] With reference to FIGS. 31-33, another example loudspeaker isdepicted at reference numeral 3100. Loudspeaker 3100 includes a casement3102 having a diaphragm 3104 coupled to the casement 3102. Loudspeaker3100 also includes a frame 3106 having a plurality of magnets 3108coupled to a body portion 3110 of frame 3106.

[0117] Casement 3102 includes a pair of generally parallel side rails3112 orthogonally intersected by a pair of generally parallel end rails3114. Diaphragm 3104 may be embedded within a portion of each of siderail 3112 and end rail 3114. Casement 3102 may be coupled to frame 3106to position diaphragm 3104 a predetermined distance from magnets 3108.Casement 3102 may be coupled to frame 3106 using a variety of techniquessuch as ultrasonic welding, snap fit connections, mechanical fasteners,adhesive bonding or any other suitable connection method.

[0118] Alternatively, the casement may be coupled with the frame by asecuring device in the form of a retainer as shown in FIG. 35. Anexample loudspeaker 3500 includes a retainer 3502, a casement 3504 and aframe 3506. Casement 3504 includes a flange 3508 radially protrudingfrom the perimeter of casement 3504. Similarly, frame 3506 includes aflange 3510 radially extending from a body portion 3512 of frame 3506.Retainer 3502 is the securing device to couple casement 3504 with frame3506. In the illustrated example, retainer 3502 has a generally c-shapedcross section capable of engaging flanges 3508 and 3510. Rigidengagement of flanges 3508 and 3510 interconnects casement 3504 andframe 3506.

[0119] As shown on the right side of FIG. 35, another example retainer3502 may also include loudspeaker mounting provisions. The illustratedretainer 3502 includes a flange 3514 having an aperture 3516 extendingthrough the flange 3514. The use of the loudspeaker mounting provisionson retainer 3502 improves design flexibility. For example, a frame andmagnet assembly may be designed for use with a variety of differentlyshaped retainers 3502 configured to mount loudspeakers within certainvehicles or enclosures.

[0120] To assemble a loudspeaker equipped with retainer 3502, frame 3506and casement 3504 may be placed within an injection mold cavity. Moltenresin may be injected within the cavity to form retainer 3502. Aftersolidification of the resin, completed loudspeaker 3500 may be ejectedfrom the mold cavity.

[0121] With specific reference to FIGS. 36 and 37, another exampleloudspeaker 3600 includes an example casement and diaphragm subassembly3602 and an example frame and magnet assembly 3604. Casement anddiaphragm subassembly 3602 includes a casement 3606 and diaphragm 3608.Casement 3606 includes a pair of side rails 3610 and a pair of end rails3612 interconnected to one another to define an aperture 3614. Siderails 3610 and end rails 3612 include apertures 3615 extending throughthe side rails 3610 and the end rails 3612.

[0122] Frame and magnet subassembly 3604 includes a frame 3616 having abody 3617 with a plurality of stakes 3618 protruding from the body 3617.The frame 3616 also includes a plurality of catches 3620 extending frombody 3617. The illustrated catch 3620 includes a barb 3622. Duringcoupling of casement and diaphragm subassembly 3602 to frame and magnetsubassembly 3604, barb 3622 may engage casement 3606. In addition,stakes 3618 may protrude through apertures 3615. A subsequent heatstaking or melting process may be performed to deform the ends of stakes3618 to form a cap 3700. The cap 3700 may maintain coupling of casementand diaphragm subassembly 3602 to frame and magnet subassembly 3604. Inother examples, any other form of fastening mechanism such as anadhesive, a latch, hook, welding, a snap-fit connection, etc. may beused to couple the casement and diaphragm subassembly 3602 to frame andmagnet subassembly 3604.

[0123] To manufacture loudspeaker 3600, an example injection mold 3400as shown in FIG. 34 may be used. Injection mold 3400 includes astationary plate 3402 and a movable plate 3404. Stationary plate 3402and movable plate 3404 define a cavity 3406 in communication with a gate3408. Gate 3408 serves as an inlet for a molten resin material 3410.Movable plate 3404 includes a gas permeable plate 3412 inserted within agas impermeable die body 3414. A vacuum channel 3416 is positioned alonga back surface 3418 of plate 3412. Vacuum channel 3416 is coupled to avacuum source (not shown). Movable plate 3404 includes a plurality ofpins 3420 extending upwardly from a substantially planar surface 3421.Each pin 3420 includes an upper surface 3422 which engages a lowersurface 3424 of stationary plate 3402 when injection mold 3400 isclosed.

[0124] An oversized, work-in-progress, example diaphragm 3425 isillustrated as inserted within injection mold 3400 in FIG. 34. Oversizeddiaphragm 3425 includes a center portion 3426 surrounded by a perimeterportion 3428. Perimeter portion 3428 includes an offage portion 3430extending beyond the edge of cavity 3406. Finished diaphragm 3608, shownin FIGS. 36 and 37, is created by trimming offage portion 3430 fromoversized diaphragm 3425. Diaphragm 3608 also includes a plurality ofapertures 3432. Upon insertion of diaphragm 3425, the plurality of pins3420 extend through apertures 3432 and diaphragm 3425 rests on planarsurface 3421.

[0125] During manufacture of the casement and diaphragm subassembly,perimeter portion 3428 of diaphragm 3425, specifically offage portion3430, may be clamped between stationary plate 3402 and movable plate3404 of injection mold 3400. After perimeter portion 3428 is clamped,center portion 3426 may be displaced to introduce a tension to diaphragm3425. While diaphragm 3608 is under tension, molten plastic may beinjected into cavity 3406 to form side rails 3610 and end rails 3612.During the injection process, perimeter portion 3428 may partially meltand bond with the material forming casement 3606. The casement materialmay then be cooled and solidified. The tensioned diaphragm 3608 moldedto casement 3606 may now be removed from the injection mold 3400. Offageportion 3430 may be trimmed to produce the final casement and diaphragmassembly 3602 as shown in FIG. 36. The casement and diaphragmsubassembly may be utilized as a component within many different speakerdesigns including loudspeakers having metal frames as previouslydescribed or molded frames similar to frame 3616.

[0126] It should be appreciated that a number of different devices suchas pins, clamps, notches or stops may be used to temporarily fix offageportion 3430 while center portion 3426 is tensioned. One exampleretention device is shown in FIG. 38 in the form of a pin 3800. Pin 3800may extend through an aperture 3802 and through diaphragm 3425. Aperture3802 may be located in offage portion 3430. Pin 3800 may be positionedto retain the perimeter portion of diaphragm 3425 during tensioning.Although illustrated as a pin, a variety of devices such as clamps, pinsor stops may be used to locate and retain the perimeter portion of thediaphragm 3425 during tensioning.

[0127]FIG. 38 also illustrates a portion of an example injection moldthat is depicted at reference numeral 3804. Mold 3804 includes astationary half 3806 having a ridge 3808 protruding downwardly from thestationary half 3806. Mold 3804 also includes a movable half 3810 havinga trough 3812 extending about the periphery of the mold. During moldclosure, ridge 3808 contacts diaphragm 3425 and forces diaphragm 3425 toenter trough 3812. During this process, diaphragm 3425 is tensioned andretained under tension. To assure a sufficient amount of tension isgenerated in diaphragm 3425, pins 3800 may be positioned outboard ofridge 3808 and trough 3812 to retain the perimeter portion of diaphragm3425 during tensioning. As previously mentioned, molten resin is theninjected to form casement 3606.

[0128] With reference to FIG. 39, another example loudspeaker isdepicted at reference numeral 3900. Loudspeaker 3900 includes a frame3902 having a plurality of magnets 3904 coupled to a body portion 3906of frame 3902. An example elastic bumper 3908 may be coupled to frame3902. Elastic bumper 3908 may be constructed from a material capable ofrecovering size and shape after deformation such as a solid elastomericmember, closed cell foam or any other resilient material. Elastic bumper3908 may be coupled to and extend substantially about the perimeter offrame 3902.

[0129] Elastic bumper 3908 may be attached to frame 3902 using adhesivesor mechanical fasteners. Elastic bumper 3908 may also be molded to frame3902 using an injection mold. For example, where the frame isconstructed from injection molded plastic, frame 3902 may first beformed in a mold. An elastic material, such as polyvinyl may then beinjected into the mold to form elastic bumper 3908 on frame 3902.Alternatively, elastic bumper 3908 may be formed in a different mold andcoupled with frame 3902 by adhesives, mechanical fasteners, welding,etc.

[0130] During assembly of example loudspeaker 3900, elastic bumper 3908may be compressed by applying an external force in the directionillustrated by arrows 3910. The compression force may be maintainedwhile a diaphragm 3912 is coupled to bumper 3908 by adhesives,mechanical fasteners, welding, etc. Once diaphragm 3912 is fixedlycoupled with elastic bumper 3908, the external force compressing elasticbumper 3908 may be removed. Elastic bumper 3908 may then attempt toreturn to the originally uncompressed shape, but is resisted bydiaphragm 3912. An equilibrium condition is reached resulting intensioning of diaphragm 3912. Elastic bumpers 3908 may extendcircumferentially about the entire periphery of frame 3902.Alternatively, the elastic bumpers 3908 may be represented by pluralityof small elastomeric portions selectively positioned along oppositesides of frame 3902.

[0131]FIG. 40 shows another example loudspeaker 4000 that includesanother example of at least one elastic bumper 4002. The elastic bumper4002 of this example may be a hollow member formed with resilientmaterial. Similar to the FIG. 39, the elastic bumper 4002 may be coupledto a perimeter portion of frame 3902.

[0132] During assembly of loudspeaker 4000, elastic bumpers 4002 may becompressed by applying an external force in the direction of arrows4004. The compression force may be maintained while diaphragm 3912 ismechanically coupled to elastic bumper 4002. Once diaphragm 3912 isfixed to elastic bumper 4002, the external force compressing elasticbumper 4002 may be removed. The tendency of elastic bumper 4002 toreturn to the uncompressed state is resisted by diaphragm 3912. Anequilibrium condition is reached resulting in tensioning of diaphragm3912.

[0133] While various embodiments of the invention have been described,it will be apparent to those of ordinary skill in the art that otherembodiments and implementations are possible that are within the scopeof this invention. Accordingly, the invention is not restricted exceptin light of the attached claims and their equivalents.

What is claimed is:
 1. An electro-dynamic loudspeaker comprising: adiaphragm having an electrical conductor coupled thereto; a molded framehaving a body defining a mounting plane; a plurality of magnets at leastpartially embedded in the body of the frame, where the diaphragm iscoupled to the mounting plane, and where each of the magnets is offsetfrom the mounting plane.
 2. The electro-dynamic loudspeaker of claim 1where each of the magnets has an upper surface, and where the uppersurface of each of the magnets is positioned to be substantiallycoplanar with the upper surface of each of the other magnets.
 3. Theelectro-dynamic loudspeaker of claim 1 where each of the magnetsincludes an upper surface aligned with an upper surface of the body ofthe frame.
 4. The electro-dynamic loudspeaker of claim 1 where at leasttwo of the magnets have different thickness.
 5. The electro-dynamicloudspeaker of claim 1 further comprising an electrical terminal atleast partially embedded within a portion of the frame.
 6. Theelectro-dynamic loudspeaker of claim 5 where the electrical terminalincludes a male prong extending from the body of the frame.
 7. Theelectro-dynamic loudspeaker of claim 6 where the frame includes a wallpartially enclosing the male prong portion of the electrical terminal.8. The electro-dynamic loudspeaker of claim 5 where the electricalterminal includes an end portion extending beyond the surface of theframe, wherein the end portion is electrically coupled to the electricalconductor.
 9. The electro-dynamic loudspeaker of claim 8 where theelectrical terminal includes a male prong portion extending from thebody of the frame, and where the electrical terminal includes anintermediate portion positioned between the end portion and the maleprong portion, the intermediate portion being embedded within the frame.10. An electro-dynamic loudspeaker comprising: a molded plastic frame; afirst magnet and a second magnet integrally molded into the frame; andthe first and second magnets each having a first surface and a secondsurface, where the first surface of each of the first and second magnetsis aligned in substantially a single plane.
 11. The electro-dynamicloudspeaker of claim 10 where the first magnet is positioned in a firstrow and the second magnet is positioned in a second row to form amagnetic field between the first and second magnets.
 12. Theelectro-dynamic loudspeaker of claim 10 where the first magnet ispositioned in the frame with opposite polarity with respect to thepolarity of the second magnet.
 13. The electro-dynamic loudspeaker ofclaim 10 where the first magnet comprises a plurality of magnets in afirst row and the second magnet comprises a plurality of magnets in asecond row.
 14. The electro-dynamic loudspeaker of claim 10 where thefirst and second magnets comprise a plurality of longitudinallyextending members positioned end-to-end in a first row and a second row,respectively in the frame.
 15. The electro-dynamic loudspeaker of claim10 where the first surface of the first and second magnets is coplanarwith a surface of the frame, and the second surface of the first andsecond magnets is embedded in the molded plastic frame.
 16. Theelectro-dynamic loudspeaker of claim 10 where each of the first andsecond magnets includes a slot, where the slot is filled with plasticwhen the first and second magnets are embedded in the frame.
 17. Theelectro-dynamic loudspeaker of claim 10, further comprising a diaphragm,where the diaphragm is mounted to the frame in a state of tension and isspaced apart from the first and second magnets by a determined distance.18. The electro-dynamic loudspeaker of claim 17, where the diaphragmcomprises a thin film coupled with the frame that is a movable membranecapable of producing sound.
 19. The electro-dynamic loudspeaker of claim18, where the thin film is of only one-piece construction.
 20. Anelectro-dynamic loudspeaker comprising: a plurality of longitudinallyextending magnets; and a frame having a first surface and a secondsurface, where the magnets are embedded in the first surface of theframe in a plurality of spaced apart rows to extend longitudinally alongthe first surface, where the magnets also extend partially through theframe towards the second surface.
 21. The electro-dynamic loudspeaker ofclaim 20 where the first surface is an inner surface of the frame thatis positionable adjacent to a diaphragm and the second is an outersurface of the frame.
 22. The electro-dynamic loudspeaker of claim 20where the frame is a bowed frame.
 23. The electro-dynamic loudspeaker ofclaim 20 where the frame is elastically deformable to tension adiaphragm.
 24. The electro-dynamic loudspeaker of claim 20 where theframe includes a plurality of apertures extending from the first surfaceto the second surface, where the rows of magnets are positioned betweenrows of the apertures.
 25. The electro-dynamic loudspeaker of claim 20where the magnets are embedded in the frame to be substantially coplanarwith the first surface of the frame.
 26. The electro-dynamic loudspeakerof claim 24 where the magnets non-uniformly extend toward the secondsurface to remain coplanar with the first surface.
 27. Theelectro-dynamic loudspeaker of claim 20 where the magnets are generallyrectangular and are positioned end-to-end in the rows.
 28. A method ofconstructing an electro-dynamic loudspeaker comprising: placing magnetswithin a cavity of an injection mold; enclosing the cavity; injectingmolten resin about at least a portion of the magnets to partiallyencapsulate the magnets within the resin; and solidifying the resin toform a frame having the magnets encapsulated therein.
 29. The method ofclaim 28 where injecting molten resin comprises filling a slot includedin each of the magnets with the molten resin to retain the magnets inthe resin.
 30. The method of claim 28 further comprising placing anelectrical terminal within the open mold cavity prior to injectingmolten resin.
 31. The method of claim 30 further comprising masking aportion of the electrical terminal to define an encapsulated portion ofthe electrical terminal and an exposed portion of the electricalterminal protruding from the frame after the resin has been solidified.32. The method of claim 28 further comprising attaching a diaphragm tothe frame.
 33. The method of claim 284 further comprising molding thediaphragm to the frame during the molten resin injection process. 34.The method of claim 28 where placing the magnets comprises positioningthe magnets end-to-end in rows in the mold.
 35. The method of claim 28where placing the magnets comprises positioning the magnets with anupper surface of the magnets in substantially a single plane.
 36. Themethod of claim 28 where partially encapsulating the magnets comprisesforming the surface of the resin coplanar with a surface of the magnets.